The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIGS. 1 and 2, seats in a vehicle are typically attached by a seat track assembly 10 to a floor of the vehicle. The seat track assembly 10 provides for fore-aft adjustment and typically includes a first track portion 12 arranged in parallel with a second track portion 14. The first and second track portions 12 and 14 each include upper and lower tracks 15 and 16, respectively. The lower tracks 16 are connected to the vehicle. The upper tracks 15 move fore and aft relative to the stationary lower tracks 16. A third track portion 17 is connected generally perpendicular to the upper tracks 15 of the first and second track portions 12 and 14, respectively.
The third track portion 17 includes a motor 18 connected by drive cables 20 and 22 (shown housed in tubes 23) to first and second gearboxes 24 and 26 arranged in the first and second track portions 12 and 14, respectively. First and second lead screws 28 and 30 pass through first and second brackets 32 and 34 and the first and second gearboxes 24 and 26, respectively. End brackets 36 and 38 connect ends of the first and second lead screws 28 and 30 to the vehicle.
The first and second gearboxes 24 and 26 include worms and worm gears. The worms may have a lead angle of around 15°. Gear reduction occurs in the first and second gearboxes 24 and 26 at each of the first and second track portions 12 and 14, respectively, which tends to increase sound and vibration resonance. Multiple gear reductions may create a lead-lag situation in the power system and increase droning and noise variation.
The drive cables 20 and 22 may be rotated at relatively high speeds, such as 1500-3000 rpm, which tends to induce gear mesh noise or cable whip. The drive cables 20 and 22 are also sensitive to misalignment between the first and second track portions 12 and 14. Noise reduction measures for the drive cables 20 and 22 such as the tubes 23 and flocking increase friction and power loss. Also, torque translation from the motor 18 to the first and second gearboxes 24 and 26 at higher rotational speeds before gear reduction at the first and second gearboxes 24 and 26 erodes power translation.
The seat track assembly 10 must be a rigid structure to negate misalignment and sound/vibration resonance. Also, lubrication within the seat track assembly 10 can result in contamination due to the location of the seat adjuster within the vehicle. Different dampening measures must be used to reduce noise and vibration.